Resolution of Generic Safety Issues: Issue 203: Potential Safety Issues with Cranes That Lift Spent Fuel Casks ( NUREG-0933, Main Report with Supplements 1–34 )
This issue was identified by an NMSS engineer in December 2006 and addressed concerns about potential safety issues with cranes that are used to lift spent fuel casks at nuclear power plants. The areas of concern involved questions about the technical adequacy or programmatic effectiveness of existing regulatory programs and activities that are implemented through the NRC reactor oversight process (ROP). These were as follows:
(1) Cranes that do not conform to original design specifications: load drop analysis is not part of design basis, inadequate design basis documentation/information from parts vendors, and NRC inspection responsibilities for review of load drop analysis are unclear.
(2) Cranes that licensees modified without performing safety evaluation reviews required by 10 CFR 50.59, which may indicate that some licensees assume that these reviews are not required.
(3) Cranes that have had inadequate maintenance: overlooks important operating experience, invalidates single-failure proof capability, and tolerated by deficient NRC requirements for maintenance.
(4) Cranes that are not single-failure proof or lack credible validation for single-failure proof status have been used without adequate load path protection, or other mitigative measures, and this condition is not adequately considered in NRC's probabilistic risk assessment of crane events.
RIS 2005-251890 describes the NRC's regulatory position with respect to the areas of concern identified in this issue, and identifies the design and inspection bases for cranes having the potential to impact SSCs important to safety. RIS 2005-251890 addresses: (1) single-failure-proof cranes, including guidelines for upgrading cranes to single-failure-proof status as well as for crane inspection, testing, and maintenance; and (2) conditions requiring load drop analyses. RIS 2005-251890 provides guidance on load drop analysis assumptions and methods, and incorporated operating experience from NUREG-1774,1846 including results from staff work associated with Issue186, "Potential Risk and Consequences of Heavy Load Drops in Nuclear Power Plants," which formed the risk-informed basis for its use by the NRC to clarify NRC guidelines for licensees' programs for the control of heavy loads.
One possible net impact of the four areas of concern is that licensees have maintained inadequate control of changes to cranes over long periods of time. Sources of crane changes to consider include: design modifications, parts and information from vendors, aging, maintenance (or lack thereof), and incorporation of lessons learned from operating experience. Potential consequences from licensees' inadequate control of these changes may result in conditions where cranes no longer conform to original design specifications, conditions that invalidate load drop analysis or the single-failure-proof status of cranes. Licensees' control of the design basis of cranes that provide functions important to safety is clearly within the purview of the ROP inspection procedures. In addition, guidance from RIS 2005-251890 describes the NRC's regulatory position that licensees can maintain adequate defense-in-depth through the use of single-failure-proof cranes, by providing various appropriate forms of load path protection, or by performing adequate load drop analyses that demonstrate acceptable consequences. Thus, licensees may choose among these alternatives to maintain adequate defense-in-depth (i.e., they are not specifically obligated to maintain original design basis, to perform load drop analysis, or to provide load path protection for cranes providing important to safety functions). Again, these considerations are part of the existing regulatory framework.
The four areas of concern identified in this issue are covered under existing inspection procedures of the ROP. The guidance provided to licensees in RIS 2005-251890 clearly describes NRC's regulatory position for licensees' control of heavy loads programs covering the areas of concern identified. Therefore, the areas of concern represented licensee compliance issues and, as such, were not suitable for further assessment in the Generic Issues Program, as delineated in MD 6.4. The concerns were entered into the ROP Feedback Program, in accordance with Inspection Manual Chapter 0801, and assigned the ROP Feedback Form Item Number 60854-1-1113. Thus, this issue was DROPPED from further pursuit as a generic issue.1891